British general and historian who fought in the Napoleonic Wars, particularly in the Peninsular War in Spain and Portugal; he wrote the popular History of the War in the Peninsula . . . , 6 vol. (1828–40), based partly on his own combat experiences and partly on information supplied by two commanders in that conflict, the Duke of Wellington and the French marshal Nicolas-Jean de Dieu Soult.

During the Peninsular War, Napier fought in the major battles of Fuentes de Oñoro, Salamanca, and the Nivelle River and was wounded several times. He retired in 1819.

Napier began his History in 1823. His account was widely acclaimed for its vigorous battle scenes and powerful style, but it was also attacked for its inaccuracy and bias. Nonetheless, it remained the standard work on the subject until the publication of Sir Charles Oman's History of the Peninsular War (1902–30). Napier was knighted in 1848. He later edited and wrote two books about his brother Sir Charles James Napier, conqueror of Sind.